Scientific Symposium Presentation Abstracts
September 19
Dr. Eric S. Kasischke: Increasing Vulnerability of Alaska’s Boreal Forest as a Result of Climate Warming and the Changing Fire Regime
Since the early 1960s, Interior Alaska has experienced a 1.0 to 1.5ºC (about 1.8 to 2.7ºF) warming (Chapin et al., 2005), and should this trend continue, there is little doubt that there will be a shift in the distribution of boreal forest ecosystems throughout this region, with a decrease in coniferous forests and an increase in deciduous forests and grasslands (Chapin et al., 2006). However, the processes controlling the rate change in these ecosystems are complex because the dominant forest type, black spruce (Picea mariana), contains deep layers of surface organic matter overlying permafrost. As a result, deciduous species are not successful in establishing dominance at a site unless the surface organic matter is consumed during the wildfires that are common to this region (Kasischke et al., 2002), which not only expose mineral soils required for successful germination and growth of aspen and birch seedlings (Johnstone and Kasischke, 2005), but also warm or eliminate permafrost at a site (Kasischke and Johnstone, 2005).
Coincident with the recent warming trend in Alaska and Canada, there has also been a doubling of the annual burned area in wildfires between the 1960s/1970s and 1980s/1990s (as a result of the increase in frequency of large fire years at sub-regional scale; Kasischke and Turetsky, 2006) and a warming of permafrost (Osterkamp, 2005). The increase in fire frequency has been accompanied by a shift to seasonality of burning, with more fire occurring during August and September. In Alaskan black spruce forests with permafrost, the seasonal thawing of soils controls the moisture content of the surface organic layers; hence, fires that occur late in the growing season result in the deep burning of organic matter required for the establishment of deciduous species. One scenario that researchers are now focusing on involves the combined effects of climate warming, changes to the fire regime, and permafrost warming, which together will accelerate changes to the boreal forest.
The lands and bodies of water of Interior Alaska provide the habitat for many fish, bird, and animal species whose distribution and abundance have evolved along the terrestrial ecosystems that are unique to the boreal region. Interior Alaska is home to a large population of Native peoples whose livelihood depends upon use of its natural resources to provide a wide range of subsistence services. Many of these ecosystem services are also used by non-native peoples. As a result, future changes to the terrestrial ecosystems of this region as a result of climate warming and changes to the fire regime will have impacts on human society (Natcher, 2004; Chapin et al., 2004).
Chapin, F.S., III, G. Peterson, F. Berkes, T.V. Callaghan, P. Angestam, M. Apps, C. Beier, Y. Bergeron, A.-S. Crepin, K. Danell, T. Elmqvist, C. Folke, B. Forbes, N. Fresco, G. Juday, J. Niemela, A. Shvidenko, and G. Whiteman, 2004: Resilience and vulnerability of northern regions to social and environmental change, Ambio, 33, 344-349.
Chapin, F.S., III, M. Sturm, M.C. Serreze, J.P. McFadden, J.R. Key, A.H. Lloyd, A.D. McGuire, T.S. Rupp, A.H. Lynch, J.P. Schimel, J. Beringer, W.L. Chapman, H.E. Epstein, E.S. Euskirchen, L.D. Hinzman, G. Jia, C.L. Ping, K.D. Tape, C.D.C. Thompson, D.A. Walker, and J.M. Welker, 2005: Role of land-surface changes in Arctic summer warming, Science, 310, 657-660.
Chapin III, F.S., M.W. Oswood, K. Van Cleve, L.A. Viereck, and D.L. Verbyla (editors), 2006: Alaska’s Changing Boreal Forest, pp. 354, Oxford University Press, New York.
Johnstone, J.F., and E.S. Kasischke, 2005: Stand-level effects of burn severity on post-fire regeneration in a recently-burned black spruce forest, Can Journal of Forest Research, 35, 2151-2163.
Kasischke, E.S., and J.F. Johnstone, 2005: Variation in post-fire organic layer thickness in a black spruce forest complex in Interior Alaska and its effects on soil temperature and moisture, Can Journal of Forest Research, 35, 2164-2177.
Kasischke, E.S., and M.R. Turetsky, 2006: Recent changes in the fire regime across the North American boreal region- spatial and temporal patterns of burning across Canada and Alaska, Geophysical Research Letters, 33, L09703, doi:10.1029/2006GL025677.
Kasischke, E.S., D. Williams, and D. Barry, 2002: Analysis of the patterns of large fires in the boreal forest region of Alaska, International Journal of Wildland Fire, 11, 131-144.
Natcher, D.C., 2004: Implications of fire policy on native land use in Yukon Flats, Alaska, Human Ecology, 32, 421-441.
Osterkamp, T.E., 2005: The recent warming of permafrost in Alaska, Global and Planetary Change, 49, 187-202.
